Adding correct installation step

gnongsie · web-flow · commit 1824ef0ea001 · 2018-11-15T12:39:58.000+05:30
diff --git a/README.md b/README.md
@@ -19,7 +19,7 @@ You can also run each sample directly from the command line.
 ```
 * Install the [Authorize.Net Ruby SDK](https://www.github.com/AuthorizeNet/sdk-ruby):
 ```
-    $ git clone https://github.com/AuthorizeNet/sample-code-ruby
+    $ gem install authorizenet
 ```
 
 * Run the individual samples by name. For example:  
